Phosphonite containing catalysts for hydroformylation processes

ABSTRACT

Novel trivalent organophosphonite ligands having the structure of general formula (I): 
                         
wherein R is an alkyl or aryl group containing 1 to 30 carbon atoms; Ar 1  and Ar 2  are aryl groups containing 4 to 30 carbon atoms; R1 to R6 are H or alkyl or aryl hydrocarbon radicals containing 1 to 40 carbon atoms; and X is a connecting group or a simple chemical bond, were developed and found to be very active for hydroformylation processes for ethylenically unsaturated substrates. Catalyst solutions prepared from these ligands with a Rh metal show an unusual “ligand acceleration effect” for simple alkenes, i.e., the hydroformylation activity increases as the concentration of ligand increases, and are capable of producing linear or branched aldehydes under typical hydroformylation conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 61/016,665 filed on Dec. 26, 2007, the disclosure of which isincorporated herein by reference to the extent it does not contradictthe disclosures herein.

FIELD OF THE INVENTION

This invention generally relates to phosphonite compounds, a catalystsolution containing the same, and a hydroformylation process using thecatalyst solution.

BACKGROUND OF THE INVENTION

The hydroformylation reaction, also known as the oxo reaction, is usedextensively in commercial processes for the preparation of aldehydes bythe reaction of one mole of an olefin with one mole each of hydrogen andcarbon monoxide. One use of the reaction is in the preparation ofnormal- and iso-butyraldehyde from propylene. The ratio of the amount ofthe normal aldehyde product to the amount of the iso aldehyde producttypically is referred to as the normal-to-iso (N:I) or thenormal-to-branched (N:B) ratio. In the case of propylene, the normal-and iso-butyraldehydes obtained from propylene are in turn convertedinto many commercially valuable chemical products such as, for example,n-butanol, 2-ethyl-hexanol, n-butyric acid, iso-butanol, neo-pentylglycol, 2,2,4-trimethyl-1,3-pentanediol, and the mono-isobutyrate anddi-isobutyrate esters of 2,2,4-trimethyl-1,3-pentanediol.

In most cases, a phosphorus ligand-containing catalyst is used for theoxo process (so called “low pressure hydroformylation process”).Phosphorus ligands not only can stabilize metal, but can also regulatethe catalyst activity and selectivity. Oxo catalyst activity oftendecreases as the amount of phosphorus ligands increases while thecatalyst stability increases with increasing amounts of ligand.Therefore, there exists an optimum concentration of phosphorus ligandsfor operating an oxo reactor which is the result of a tradeoff betweenincreased stability and reduced catalyst activity.

In reality, the gradual loss of phosphorus ligands is inevitable becauseof decomposition and other reasons. In some cases, such as overflowreactors, the decomposition of ligands may be worsened due to the hightemperature required to separate catalysts from products. In practice,fresh phosphorus ligands have to be replenished to the reactor on aregular basis to compensate for the loss of ligands.

Thus, there is a need in the art for ligands that not only stabilize thecatalyst at higher concentrations, but also can increase the catalystactivity at such concentrations.

SUMMARY OF THE INVENTION

A class of ligands has been discovered that can substantially increasethe Rh catalyst activity by simply increasing the novel phosphoniteligand concentration. In some embodiments, the ligand offers one or morebenefits such as enhanced catalyst stability, increased production rate,and reduced daily operation costs due to eliminated needs forreplenishing ligands.

In one aspect, the present invention provides a phosphonite compoundhaving the structure of formula (I):

wherein

R is an alkyl or aryl group containing 1 to 30 carbon atoms;

Ar₁ and Ar₂ are each independently aryl groups containing 4 to 30 carbonatoms;

R1 to R6 are each independently selected from H and hydrocarbylcontaining 1 to 40 carbon atoms; and

X is

-   -   (i) a chemical bond directly between ring carbon atoms of each        aromatic group,    -   (ii) a heteroatom, or    -   (iii) a group having the formula

wherein R15 and R16 are each independently selected from hydrogen andalkyl or aryl having up to 10 carbon atoms.

In a second aspect, the present invention provides a catalyst solutioncomprising:

(a) a phosphonite compound;

(b) a Group VIII metal or rhenium; and

(c) a hydroformylation solvent,

wherein the phosphonite compound has the structure of formula (I):

wherein

R is an alkyl or aryl group containing 1 to 30 carbon atoms;

Ar₁ and Ar₂ are each independently aryl groups containing 4 to 30 carbonatoms;

R1 to R6 are each independently selected from H and hydrocarbylcontaining 1 to 40 carbon atoms; and

X is

-   -   (i) a chemical bond directly between ring carbon atoms of each        aromatic group,    -   (ii) a heteroatom, or    -   (iii) a group having the formula

wherein R15 and R16 are each independently selected from hydrogen andalkyl or aryl having up to 10 carbon atoms.

In a third aspect, the present invention provides a process forpreparing aldehydes, comprising contacting an olefin with hydrogen andcarbon monoxide, under hydroformylation conditions, in the presence ofthe catalyst solution herein described.

DETAILED DESCRIPTION OF THE INVENTION

New phosphonite compounds have been discovered that are useful asligands in hydroformylation reactions. The invention thus provides newphosphonite compounds. The invention further provides highly activecatalyst solution for use in hydroformylation reactions.

The catalyst solution comprises:

(a) a phosphonite compound;

(b) a Group VIII metal or rhenium; and

(c) a hydroformylation solvent.

The phosphonite compound according to the invention has the structure offormula (I):

wherein

R is an alkyl or aryl group containing 1 to 30 carbon atoms;

Ar₁ and Ar₂ are each independently aryl groups containing 4 to 30 carbonatoms;

R1 to R6 are each independently selected from H and hydrocarbylcontaining 1 to 40 carbon atoms; and

X is

-   -   (i) a chemical bond directly between ring carbon atoms of each        aromatic group,    -   (ii) a heteroatom, or    -   (iii) a group having the formula

wherein R15 and R16 are each independently selected from hydrogen andalkyl or aryl groups having up to 10 carbon atoms. In some embodiments,R15 and R16 are each independently selected from hydrogen and alkylgroups having one or two carbon atoms. In some embodiments, R15 and R16are each independently selected from hydrogen and methyl groups.

The heteroatom can be any atom other than carbon that can form the bondswith the two aryl rings as shown in Formula (I) without compromising theefficacy of the ligand. In some embodiments, the heteroatom is selectedfrom sulfur, oxygen, nitrogen, and silicon, provided that the siliconand nitrogen will have additional substituents bonded thereto tocomplete the atoms bonding capability. Substituents which are acceptableinclude alkyl groups of 1 to 20 carbon atoms and aromatic groups of 6 to20 carbon atoms. In some embodiments, the heteroatom is selected from O,Si, and N, again, with additional atoms bonded to a Si or N.

R is a hydrocarbyl group selected from unsubstituted and substitutedalkyl, cycloalkyl, and aryl groups containing 1 to about 30 carbonatoms. In some embodiments the total carbon content of R is in the rangeof about 1 to 20 carbon atoms. Examples of the alkyl groups that R canrepresent include methyl, ethyl, butyl, pentyl, hexyl, 2-ethylhexyl,octyl, decyl, dodecyl, octadecyl and various isomers thereof. The alkylgroups may be substituted, for example, with up to two substituents suchas alkoxy, cycloalkoxy, formyl, alkanoyl, cycloalkyl, aryl, aryloxy,aroyl, carboxyl, carboxylate salts, alkoxycarbonyl, alkanoyloxy, cyano,sulfonic acid, sulfonate salts, and the like. Cyclopentyl, cyclohexyland cycloheptyl are examples of the cycloalkyl groups that R canrepresent. The cycloalkyl groups may be substituted with alkyl or any ofthe substituents described with respect to the possible substitutedalkyl groups. In some embodiments, the unsubstituted or substitutedalkyl and cycloalkyl groups that R can represent are alkyls of up toabout 8 carbon atoms, benzyl, cyclopentyl, cyclohexyl, and cycloheptyl.

Examples of the aryl groups that R can represent include carbocyclicaryls such as phenyl, naphthyl, anthracenyl, and substituted derivativesthereof. Examples of the carbocyclic aryl groups that R can representinclude the radicals having the formulas (II) to (IV):

wherein R7 and R8 may represent one or more substituents independentlyselected from alkyl, alkoxy, halogen, cycloalkoxy, formyl, alkanoyl,cycloalkyl, aryl, aryloxy, aroyl, carboxyl, carboxylate salts,alkoxy-carbonyl, alkanoyloxy, cyano, sulfonic acid, sulfonate salts, andthe like. In some embodiments, the alkyl moiety of the aforesaid alkyl,alkoxy, alkanoyl, alkoxycarbonyl, and alkanoyloxy groups contains up toabout 8 carbon atoms. Although it is possible for m to represent 0 to 5and for n to represent 0 to 7, the value of each of m and n will notexceed 2. In some embodiments, R7 and R8 represent lower alkyl groups,i.e., straight-chain and branched-chain alkyl of up to about 4 carbonatoms, and m and n each represent 0, 1, or 2.

Optionally, the hydrocarbyl groups represented by R can be selected fromunsubstituted and substituted divalent alkylidene, cycloalkylidene, andarylidene groups containing up to about 30 carbon atoms. Examples ofsuch divalent hydrocarbyl groups include, but are not limited to,methylidene, ethylidene, 1,3-propylidene, 1,4-butylidene,1,5-pentylidene, 1,6-hexylidene, 1,7-heptylidene, 1,8-octyllidene,cyclohexylidene, cyclopentylidene, norbornylidene, biphenyldiyl,methylidenebis(2-phenyl), etc.

The hydrocarbyl groups represented by R1 to R4 are selected fromunsubstituted and substituted alkyl, cycloalkyl, and aryl groupscontaining up to about 40 carbon atoms. In some embodiments, the totalcarbon content of R1 to R4 is in the range of about 1 to 15 carbonatoms. Examples of the alkyl groups that R1 to R4 can represent includemethyl, ethyl, butyl, pentyl, hexyl, 2-ethylhexyl, octyl, decyl,dodecyl, octadecyl, and various isomers thereof. The alkyl groups may besubstituted, for example, with up to two substituents such as alkoxy,cycloalkoxy, formyl, alkanoyl, cycloalkyl, aryl, aryloxy, aroyl,carboxyl, carboxylate salts, alkoxycarbonyl, alkanoyloxy, cyano,sulfonic acid, sulfonate salts, and the like. Cyclopentyl, cyclohexyl,and cycloheptyl are examples of the cycloalkyl groups that R1 to R4 canrepresent. The cycloalkyl groups may be substituted with alkyl or any ofthe substituents described with respect to the possible substitutedalkyl groups. In some embodiments, the unsubstituted or substitutedalkyl and cycloalkyl groups that R1 to R4 can represent are alkyls of upto about 8 carbon atoms, benzyl, cyclopentyl, cyclohexyl, andcycloheptyl.

Examples of the aryl groups that R1 to R4 can represent includecarbocyclic aryl such as phenyl, naphthyl, anthracenyl, and substitutedderivatives thereof. Examples of the carbocyclic aryl groups that R1 toR4 can represent include radicals having the formulas (V)-(VII):

wherein R9 and R10 may represent one or more substituents independentlyselected from alkyl, alkoxy, halogen, cycloalkoxy, formyl, alkanoyl,cycloalkyl, aryl, aryloxy, aroyl, carboxyl, carboxylate salts,alkoxy-carbonyl, alkanoyloxy, cyano, sulfonic acid, sulfonate salts, andthe like. In some embodiments, the alkyl moiety of the aforesaid alkyl,alkoxy, alkanoyl, alkoxycarbonyl, and alkanoyloxy groups contains up toabout 8 carbon atoms. Although it is possible for p to represent 0 to 5and for q to represent 0 to 7, in some embodiments, the value of each ofp and q will not exceed 2. In some embodiments, R9 and R10 representlower alkyl groups, i.e., straight-chain and branched-chain alkyl of upto about 4 carbon atoms, and m and n each represent 0, 1, or 2.

The hydrocarbyl groups represented by R5 and R6 may be the same ordifferent, separate or combined, and are selected from unsubstituted andsubstituted alkyl, cycloalkyl, and aryl groups containing a total of upto about 40 carbon atoms. In some embodiments, the total carbon contentof substituents R5 and R6 is in the range of about 1 to 35 carbon atoms.Examples of the unsubstituted or substituted alkyl groups that R5 and R6can represent include methyl, ethyl, butyl, pentyl, hexyl, 2-ethylhexyl,octyl, decyl, dodecyl, octadecyl, 1-alkylbenzyl, and various isomersthereof. The alkyl groups may be substituted, for example, with up totwo substituents such as alkoxy, cycloalkoxy, formyl, alkanoyl,cycloalkyl, aryl, aryloxy, aroyl, carboxyl, carboxylate salts,alkoxycarbonyl, alkanoyloxy, cyano, sulfonic acid, sulfonate salts, andthe like. Cyclopentyl, cyclohexyl, and cycloheptyl are examples of thecycloalkyl groups that R5 and R6 individually can represent. Thecycloalkyl groups may be substituted with alkyl or any of thesubstituents described with respect to the possible substituted alkylgroups. In some embodiments the unsubstituted or substituted alkyl andcycloalkyl groups that R5 and R6 can represent are alkyls of up to about10 carbon atoms such as benzyl, 1-alkylbenzyl, cyclopentyl, cyclohexyl,and cycloheptyl, etc.

Examples of the aryl groups that R5 and R6 can represent includecarbocyclic aryl such as phenyl, naphthyl, anthracenyl, and substitutedderivatives thereof. Examples of the carbocyclic aryl groups that R5 andR5 can represent include radicals having the formulas (VIII)-(X):

wherein R11 and R12 may represent one or more substituents independentlyselected from alkyl, alkoxy, halogen, cycloalkoxy, formyl, alkanoyl,cycloalkyl, aryl, aryloxy, aroyl, carboxyl, carboxylate salts,alkoxy-carbonyl, alkanoyloxy, cyano, sulfonic acid, sulfonate salts, andthe like. In some embodiments, the alkyl moiety of the aforesaid alkyl,alkoxy, alkanoyl, alkoxycarbonyl, and alkanoyloxy groups contains up toabout 8 carbon atoms. Although it is possible for r to represent 0 to 5and for s to represent 0 to 7, in some embodiments, the value of each ofr and s will not exceed 2. In some embodiments, R11 and R12 representlower alkyl groups, i.e., straight-chain and branched-chain alkyl of upto about 10 carbon atoms, and r and s each represent 0, 1, or 2.

In some embodiments, R1 to R6 in combination or collectively mayrepresent a divalent hydrocarbyl group containing up to about 40 carbonatoms. In some embodiments, the divalent hydrocarbyl group contains fromabout 12 to 36 carbon atoms. Examples of such divalent groups includealkyl of about 2 to 12 carbon atoms, cyclohexyl, and aryl. Specificexamples of the alkyl and cycloalkyl groups include ethylene,trimethylene, 1,3-butanediyl, 2,2-dimethyl-1,3-propanediyl,1,1,2-triphenylethanediyl, 2,2,4-trimethyl-1,3-pentanediyl,1,2-cyclohexylene, and the like.

Examples of the aryl groups that Ar₁ and Ar₂ can individually representinclude carbocyclic aryl such as phenyl, naphthyl, anthracenyl, andsubstituted derivatives thereof. Examples of the carbocyclic aryl groupsthat Ar₁ and Ar₂ can represent include radicals having the formulas (XI)to (XIII):

wherein R13 and R14 may represent one or more substituents independentlyselected from alkyl, alkoxy, halogen, cycloalkoxy, formyl, alkanoyl,cycloalkyl, aryl, aryloxy, aroyl, carboxyl, carboxylate salts,alkoxy-carbonyl, alkanoyloxy, cyano, sulfonic acid, sulfonate salts, andthe like. In some embodiments, the alkyl moiety of the aforesaid alkyl,alkoxy, alkanoyl, alkoxycarbonyl, and alkanoyloxy groups contains up toabout 8 carbon atoms. Although it is possible for x to represent 0 to 5and for y to represent 0 to 7, in some embodiments, the value of each ofx and y will not exceed 2. In some embodiments, R13 and R14 representlower alkyl groups, i.e., straight-chain and branched-chain alkyl of upto about 10 carbon atoms, and x and y each represent 0, 1, or 2. In someembodiments, R13 and R14 represent lower alkyl groups, i.e.,straight-chain and branched-chain alkyl of up to about 4 carbon atoms,and x and y each represent 0, 1, or 2.

The phosphonite compounds of this invention can be prepared by anyeffective method. A variety of methods for preparing phosphonites arereported in “A Guide to Organophosphorus Chemistry”, Louis D. Quin,2000, Wiley-Interscience, pp. 62 et seq. In general, phosphonites can beprepared by methods similar to those used for preparing phosphites.Examples reported by P. G. Pringle (Chem. Comm., 2000, 961) areeffective.

The novel catalyst systems provided by the present invention comprise acombination of one or more transition metals selected from the GroupVIII metals and rhenium and one or more of the phosphonite compoundsdescribed in detail hereinabove. The transition metal may be provided inthe form of various metal compounds such as carboxylate salts of thetransition metal. In some embodiments, the metal is rhodium.

Rhodium compounds that may be used as a source of rhodium for the activecatalyst include rhodium (II) or rhodium (III) salts of carboxylicacids, examples of which include di-rhodium tetraacetate dihydrate,rhodium(II) acetate, rhodium(II) isobutyrate, rhodium(II)2-ethylhexanoate, rhodium(II) benzoate, and rhodium(II) octanoate. Also,rhodium carbonyl species such as Rh₄(CO)₁₂, Rh₆(CO)₁₆, and rhodium(I)acetylacetonate dicarbonyl may be suitable rhodium feeds. Additionally,rhodium organophosphine complexes such astris(triphenylphosphine)rhodium carbonyl hydride may be used when thephosphine moieties of the complex fed are easily displaced by thephosphonite ligands of the present invention. Other rhodium sourcesinclude rhodium salts of strong mineral acids such as chlorides,bromides, nitrates, sulfates, phosphates, and the like.

The absolute concentration of rhodium in the reaction mixture orsolution may vary from 1 mg/liter up to 5000 mg/liter or more. In someembodiments of this invention, the normal concentration of rhodium inthe reaction solution is in the range of about 20 to 300 mg/liter.Concentrations of rhodium lower than this range generally yield lowerreaction rates with most olefin reactants and/or require reactoroperating temperatures that are so high as to be detrimental to catalyststability. Concentrations above this range involve higher rhodium costs.

The ratio of gram moles phosphonite ligand to gram atoms transitionmetal can vary over a wide range, e.g., gram mole phosphonite:gram atomtransition metal ratio of about 1:1 to 500:1. For rhodium-containingcatalyst systems, the gram mole phosphonite:gram atom rhodium ratio insome embodiments is in the range of about 1:1 to 200:1 with ratios insome embodiments in the range of about 1:1 to 100:1.

No special or unusual techniques are required for preparing the catalystsystems and solutions of the present invention, although in someembodiments a catalyst of high activity is obtained if all manipulationsof the rhodium and phosphonite ligand components are carried out underan inert atmosphere, e.g., nitrogen, argon, and the like. The desiredquantities of a suitable rhodium compound and ligand are charged to thereactor in a suitable solvent. The sequence in which the variouscatalyst components or reactants are charged to the reactor is notcritical.

The hydroformylation reaction solvent may be selected from a widevariety of compounds, mixture of compounds, or materials that are liquidat the pressure at which the process is being operated. Such compoundsand materials include various alkanes, cycloalkanes, alkenes,cycloalkenes, carbocyclic aromatic compounds, alcohols, esters, ketones,acetals, ethers, and water. Specific examples of such solvents includealkane and cycloalkanes such as dodecane, decalin, octane, iso-octanemixtures, cyclohexane, cyclooctane, cyclododecane, methylcyclohexane;aromatic hydrocarbons such as benzene, toluene, xylene isomers,tetralin, cumene, alkyl-substituted aromatic compounds such as theisomers of diisopropylbenzene, triisopropylbenzene andtert-butylbenzene; alkenes and cycloalkenes such as 1,7-octadiene,dicyclopentadiene, 1,5-cyclooctadiene, octene-1,octene-2,4-vinylcyclohexene, cyclohexene, 1,5,9-cyclododecatriene,1-pentene; crude hydrocarbon mixtures such as naphtha, mineral oils andkerosene; and high-boiling esters such as2,2,4-trimethyl-1,3-pentanediol diisobutyrate. The aldehyde product ofthe hydroformylation process may also be used.

In some embodiments, the solvent is the higher boiling by-products thatare naturally formed during the process of the hydroformylation reactionand the subsequent steps, e.g., distillations, that may be required foraldehyde product isolation. The main criterion for the solvent is thatit dissolves the catalyst and olefin substrate and does not act as apoison to the catalyst. Some examples of solvents for the production ofvolatile aldehydes, e.g., butyraldehydes, are those that aresufficiently high boiling to remain, for the most part, in a gas spargedreactor. Some examples of solvents and solvent combinations that are inthe production of less volatile and non-volatile aldehyde productsinclude 1-methyl-2-pyrrolidinone, dimethyl-formamide, perfluorinatedsolvents such as perfluoro-kerosene, sulfolane, water, and high boilinghydrocarbon liquids as well as combinations of these solvents.Non-hydroxylic compounds, in general, and hydrocarbons, in particular,may be used advantageously as the hydroformylation solvent since theiruse can minimize decomposition of the phosphonite ligands.

In another aspect, the present invention provides a process forpreparing aldehydes, comprising contacting an olefin with hydrogen andcarbon monoxide, under hydroformylation conditions, in the presence ofthe catalyst solution herein described.

The reaction conditions for the process of the present invention can beconventional hydroformylation conditions. The process may be carried outat temperatures in the range of about 20° to 200° C., in someembodiments, the hydroformylation reaction temperatures are from 50° to135° C. In some embodiments, reaction temperatures range from 75° to125° C. Higher reactor temperatures can increase the rate of catalystdecomposition while lower reactor temperatures can result in relativelyslow reaction rates. The total reaction pressure may range from aboutambient or atmospheric up to 70 bars absolute (about 1000 psig). In someembodiments, pressure ranges from about 8 to 28 bars absolute (about 100to 400 psig).

The hydrogen:carbon monoxide mole ratio in the reactor likewise may varyconsiderably ranging from 10:1 to 1:10, and the sum of the absolutepartial pressures of hydrogen and carbon monoxide may range from 0.3 to36 bars absolute. The partial pressures of the ratio of the hydrogen tocarbon monoxide in the feed can be selected according to thelinear:branched isomer ratio desired. Generally, the partial pressure ofhydrogen and carbon monoxide in the reactor can be maintained within therange of about 1.4 to 13.8 bars absolute (about 20 to 200 psia) for eachgas. The partial pressure of carbon monoxide in the reactor can bemaintained within the range of about 1.4 to 13.8 bars absolute (about 20to 200 psia) and can be varied independently of the hydrogen partialpressure. The molar ratio of hydrogen to carbon monoxide can be variedwidely within these partial pressure ranges for the hydrogen and carbonmonoxide. The ratios of hydrogen-to-carbon monoxide and the partialpressure of each in the synthesis gas (syn gas—carbon monoxide andhydrogen) can be readily changed by the addition of either hydrogen orcarbon monoxide to the syn gas stream. With the phosphonite ligandsdescribed herein, the ratio of linear to branched products can be variedwidely by changing the partial pressures of the carbon monoxide in thereactor.

Any of the known hydroformylation reactor designs or configurations suchas overflow reactors and vapor take-off reactors may be used in carryingout the process provided by the present invention. Thus, a gas-sparged,vapor take-off reactor design as disclosed in the examples set forthherein may be used. In this mode of operation, the catalyst which isdissolved in a high boiling organic solvent under pressure does notleave the reaction zone with the aldehyde product taken overhead by theunreacted gases. The overhead gases then are chilled in a vapor/liquidseparator to liquefy the aldehyde product and the gases can be recycledto the reactor. The liquid product is let down to atmospheric pressurefor separation and purification by conventional technique. The processalso may be practiced in a batchwise manner by contacting the olefin,hydrogen and carbon monoxide with the present catalyst in an autoclave.

A reactor design where catalyst and feedstock are pumped into a reactorand allowed to overflow with product aldehyde, i.e. liquid overflowreactor design, is also suitable. For example, high boiling aldehydeproducts such as nonyl aldehydes may be prepared in a continuous mannerwith the aldehyde product being removed from the reactor zone as aliquid in combination with the catalyst. The aldehyde product may beseparated from the catalyst by conventional means such as bydistillation or extraction, and the catalyst then recycled back to thereactor. Water soluble aldehyde products, such as hydroxy butyraldehydeproducts obtained by the hydroformylation of allyl alcohol, can beseparated from the catalyst by extraction techniques. A trickle-bedreactor design is also suitable for this process. It will be apparent tothose skilled in the art that other reactor schemes may be used withthis invention.

The olefin used as the starting material for this invention is notparticularly limiting. Specifically, the olefin can be ethylene,propylene, butene, pentene, hexene, octene, styrene, non-conjugateddienes such as 1,5-hexadiene, and blends of these olefins. Furthermore,the olefin may be substituted with functional groups so long as they donot interfere with the hydroformylation reaction. Suitable substituentson the olefin include any functional group that does not interfere withthe hydroformylation reaction and includes groups such as carboxylicacids and derivatives thereof such as esters and amides, alcohols,nitrites, and ethers. Examples of substituted olefins include esterssuch as methyl acrylate or methyl oleate, alcohols such as allyl alcoholand 1-hydroxy-2,7-octadiene, and nitriles such as acrylonitrile.

The amount of olefin present in the reaction mixture can also vary. Forexample, relatively high-boiling olefins such as 1-octene may functionboth as the olefin reactant and the process solvent. In thehydroformylation of a gaseous olefin feedstock such as propylene, thepartial pressures in the vapor space in the reactor in some embodimentsare in the range of about 0.07 to 35 bars absolute. The rate of reactioncan be favored by high concentrations of olefin in the reactor. In thehydroformylation of propylene, the partial pressure of propylene in someembodiments is greater than 1.4 bars, e.g., from about 1.4 to 10 barsabsolute. In the case of ethylene hydroformylation, the partial pressureof ethylene in the reactor in some embodiments is greater than 0.14 barsabsolute.

This invention can be further illustrated by the following examples ofembodiments thereof, although it will be understood that these examplesare included merely for purposes of illustration and are not intended tolimit the scope of the invention. Unless otherwise indicated, allpercentages are by weight. As used throughout this application, thereference to a molecule or moiety as being “substituted” means that themolecule or moiety contains one or more substituent in place of where ahydrogen atom would be on the molecule or moiety identified. Thus, a“substituted” aryl molecule having alkyl substituents would include, forexample, an alkylbenzene such as toluene.

EXAMPLES

Synthesis of Phosphonite Ligands

Phosphonites were synthesized by reaction of phenyldicholorophosphine oralkyldicholorophosphine with corresponding substituted methylenebisphenols in the presence of triethylamine. All of the syntheses werecarried out under nitrogen.

A typical procedure follows:

Methylene bisphenol (20 mmol) was mixed with triethylamine (44 mmol) ina mixed solvent (toluene:cyclohexane 2:1) and stirred. An ice-bath wasapplied to maintain the reaction temperature below 5° C. Then, asolution of phenyldicholorophosphine or alkyldicholorophosphine (20mmol) in toluene (20 to 40 ml) was added slowly into the reactionmixture. After addition, the reaction was continued at 5° C. or lowerfor 30 min., then the temperature was raised to ambient temperature for1 hour. The reaction was heated to 50° C. for 6 to 10 hours untilcomplete disappearance of the starting bisphenol as shown by GCanalysis. The precipitate that formed was removed by filtration, and theaqueous reaction mixture was washed with water (2×20 ml) and brine (2×20ml). The organic phase was dried with anhydrous sodium sulfate. Thesolvents were removed under vacuum to afford the phosphonite compounds.All of these compounds are very soluble in common organic solvents suchas diethyl ether, THF, toluene, ethyl acetate, chloroform, etc. Reactionyields are often greater than 85%. They can be purified either byrecrystallization (methanol/toluene mixture), distillation, or columnchromatography.

Ligand A

Ligand A, having the structure shown below, was synthesized using2,2′-methylene bis(6-phenylphenol) with phenyldicholorophosphine.

Ligand “A”: O,O-2,2′-methylene bis(6-phenylphenyl)phenylphosphonite,white crystals.

Spectroscopic data of Ligand A:

³¹P NMR (CDCl₃): 168.7 ppm (s). ¹H NMR (CDCl₃): 3.65 (d, 1H), 4.61-4.65(dd, 1H), 6.91-6.95 (m, 2H), 7.13-7.49 (m, 19H) ppm.

Ligand B

Ligand B, having the structure shown below, was synthesized using2,2′-methylene bis(4,6-di(α,α-dimethylbenzyl)phenol) withphenyldicholorophosphine.

Ligand “B”: O,O-2,2′-methylenebis(4,6-bis(α,α′-dimethylbenzyl)phenyl)phenylphosphonite, white solid.

Spectroscopic data of Ligand B:

³¹P NMR (CDCl₃): 162.2 ppm (s). ¹H NMR (CDCl₃): 1.33 (s, 6H), 1.39 (s,6H), 1.68 (s, 12H), 3.23 (d, 1H), 4.23 (dd, 1H), 6.72 (m, 4H),6.93-7.30) (m, 20H) ppm.

Ligand C

Ligand C, having the structure shown below, was synthesized using2,2′-methylene bis(4,6-di(α,α-dimethylbenzyl)phenol) withcyclohexyldicholorophosphine.

Ligand “C”: O,O-2,2′-methylenebis(4,6-bis(α,α′-dimethylbenzyl)phenyl)cyclohexylphosphonite, whitesolid.

Spectroscopic data of Ligand C:

³¹P NMR (CDCl₃): 189.3 ppm (s). ¹H NMR (CDCl₃): 0.61-1.02 (m, 6H), 1.25(m, 2H), 1.47-1.55 (m, 15H), 1.66 (s, 12H), 3.14 (d, 1H), 3.99-4.03 (dd,1H), 7.03-7.27 (m, 24H) ppm.

Ligand D

Ligand D, having the structure shown below, was synthesized using2,2′-methylene bis(4,6-di(α,α-dimethylbenzyl)phenol) withmethyldicholorophosphine.

Ligand “D”: O,O′-2,2′-methylenebis(4,6-bis(α,α′-dimethylbenzyl)phenyl)methylphosphonite, white solid.

Spectroscopic data of Ligand D:

³¹P NMR (CDCl₃): 190.6 ppm (s). ¹H NMR (CDCl₃): 0.39 (d, 3H), 1.36 (s,6H), 1.57 (s, 6H), 1.68 (s, 12H), 3.15 (d, 1H), 3.99-4.03 (dd, 1H),7.00-7.29 (m, 24H) ppm.

Hydroformylation Process Set-Up

The hydroformylation process in which propylene is allowed to react withhydrogen and carbon monoxide to produce butyraldehydes was carried outin a vapor take-off reactor made up of a vertically arranged stainlesssteel pipe having a 2.5 cm inside diameter and a length of 1.2 meters.The reactor was encased in an external jacket that was connected to ahot oil machine. The reactor has a filter element welded into the sidedown near the bottom of the reactor for the inlet of gaseous reactants.The reactor contained a thermocouple which was arranged axially with thereactor in its center for accurate measurement of the temperature of thehydroformylation reaction mixture. The bottom of the reactor has a highpressure tubing connection that was connected to a cross. One of theconnections to the cross permitted the addition of non-gaseous reactantssuch as higher boiling alkenes or make-up solvents, another led to thehigh-pressure connection of a differential pressure (D/P) cell that wasused to measure catalyst level in the reactor and the bottom connectionwas used for draining the catalyst solution at the end of the run.

In the hydroformylation of propylene in a vapor take-off mode ofoperation, the hydroformylation reaction mixture or solution containingthe catalyst was sparged under pressure with the incoming reactants ofpropylene, hydrogen and carbon monoxide as well as any inert feed suchas nitrogen. As butyraldehyde was formed in the catalyst solution, itand unreacted reactant gases were removed as a vapor from the top of thereactor by a side-port. The vapor removed was chilled in a high-pressureseparator where the butyraldehyde product was condensed along with someof the unreacted propylene. The uncondensed gases were let down toatmospheric pressure via the pressure control valve. These gases passedthrough a series of dry-ice traps where any other aldehyde product wascollected. The product from the high-pressure separator was combinedwith that of the traps, and was subsequently weighed and analyzed bystandard gas/liquid phase chromatography (GC/LC) techniques for the netweight and normal/iso ratio of the butyraldehyde product.

The gaseous feeds to the reactor were fed to the reactor via twincylinder manifolds and high-pressure regulators. The hydrogen passedthrough a mass flow controller and then through a commercially available“Deoxo” (registered trademark of Englehard Inc.) catalyst bed to removeany oxygen contamination. The carbon monoxide passed through an ironcarbonyl removal bed (as disclosed in U.S. Pat. No. 4,608,239), asimilar “Deoxo” bed heated to 125° C., and then a mass flow controller.Nitrogen can be added to the feed mixture as an inert gas. Nitrogen,when added, was metered in and then mixed with the hydrogen feed priorto the hydrogen Deoxo bed. Propylene was fed to the reactor from feedtanks that were pressurized with hydrogen and was controlled using aliquid mass flow meter. All gases and propylene were passed through apreheater to ensure complete vaporization of the liquid propylene priorto entering the reactor.

Comparative Examples 1-3 Fluorophosphite Ligand

Comparative Examples 1-3 were taken directly from Puckette, “Catalysisof Organic Reactions”, Edited by S. R. Schmidt, CRC Press (2006), pp.31-38, to illustrate that hydroformylation activity decreases as themolar ratio of ligand to Rh increases (the concentration of ligandincreases). The ligand described in this literature is a fluorophosphite(Ethanox 398™,2,2′-ethylidenebis(4,6-di-tert-butylphenyl)fluorophosphite).

According to the literature, the reactions were conducted at 260 psig,115° C., 1:1 H2/CO, 54 psia C₃H₆, and 190 mL ofbis-2-ethylhexylphthalate solvent (DOP) with different amounts ofligand. The data is presented in Table 1 below and catalyst activity isexpressed as kilograms of butyraldehyde per gram Rh per hour.

Comparative Examples 4-6 Ligand A

These examples illustrate that a non-preferred, regular phenylphosphite(Ligand A) also shows a typical relationship between hydroformylationactivity and the molar ratio of ligand to Rh, i.e., the aldehydesproduction rate decreases as the ligand concentration increases.

A catalyst solution was prepared under nitrogen using a charge of 7.5 mgof rhodium (0.075 mmol, as rhodium 2-ethylhexanoate); various amounts ofLigand “A” as indicated in Table 1; 20 ml of normal butyraldehyde; and190 ml of bis-2-ethylhexylphthalate(dioctylphthalate, DOP). The mixturewas stirred under nitrogen until a homogeneous solution was obtained(heated if necessary).

The mixture was charged to the reactor in a manner described previouslyand the reactor sealed. The reactor pressure control was set at 17.9 bar(260 psig), and the external oil jacket on the reactor was heated to 85°C. Hydrogen, carbon monoxide, nitrogen, and propylene vapors were fedthrough the frit at the base of the reactor, and the reactor was allowedto build pressure. The hydrogen and carbon monoxide (H2/CO ratio was setto be 1:1) were fed to the reactor at a rate of 6.8 liters/min and thenitrogen feed was set at 1.0 liter/min. The propylene was metered as aliquid and fed at a rate of 1.89 liters/min (212 grams/hour). Thetemperature of the external oil was modified to maintain an internalreactor temperature of 85° C. The unit was operated for 5 hours andhourly samples taken. The hourly samples were analyzed as describedabove using a standard GC method. The last three samples were used todetermine the N/I ratio and catalyst activity.

The reaction conditions and the results of this work are presented inTable 1.

Examples 7-11 Ligand B

These examples illustrate a desirable nature of phosphonite Ligand B.

Hydroformylation experiments were carried out in the same manner asComparative Examples 4-6, except utilizing various amounts of Ligand“B”. The reaction conditions and the results of this work are presentedin Table 1.

Examples 12-13 Ligand C

These examples illustrate a desirable nature of phosphonite Ligand C.

Hydroformylation experiments were carried out in the same manner asComparative Examples 4-6, except utilizing various amounts of Ligand“C”. The reaction conditions and the results of this work are presentedin Table 1.

Examples 14 to 16 Ligand D

These examples illustrate a desirable nature of phosphonite Ligand D.

Hydroformylation experiments were carried out in the same manner asComparative Examples 4-6, except utilizing various amounts of Ligand“D”. The reaction conditions and the results of this work are presentedin Table 1.

TABLE 1 Effects of Ligand to Rhodium Molar Ratio on Activity andSelectivity Ligand to Rh Example Temp H2/CO Molar N/I Catalyst No.Ligand (° C.) ratio ratio Ratio Activity* C-1 fluorophosphite 115 1:114:1 1.4 15.7 C-2 fluorophosphite 115 1:1 30:1 3.1 6.6 C-3fluorophosphite 115 1:1 50:1 3.8 3.3 C-4 A 95 1:1 15:1 1.70 11.70 C-5 A95 1:1 30:1 2.25 4.25 C-6 A 95 1:1 60:1 2.40 3.87 7 B 85 1:1 15:1 2.091.80 8 B 85 1:1 30:1 1.92 3.95 9 B 85 1:1 60:1 1.83 6.41 10 B 85 1:190:1 1.79 8.14 11 B 85 1:1 180:1  1.76 8.20 12 C 85 1:1 15:1 2.79 0.1913 C 85 1:1 30:1 2.81 0.25 14 D 95 1:1 15:1 1.53 5.44 15 D 95 1:1 20:11.52 6.68 16 D 95 1:1 30:1 1.57 7.03 *Activity was determined askilograms of butyraldehydes produced per gram of rhodium per hour. Allexamples were done using 0.075 mmol of Rh.

Comparative Examples 1 through 3 illustrate that the hydroformylationreaction activity, under the same reaction temperature and pressure,steadily decreased from 15.7 to 3.3, and the N/I ratio steadilyincreased from 1.4 to 3.8 when the Ligand/Rh molar ratio increased from14:1 to 50:1.

Comparative Examples 4 through 6 again illustrate the typical,conventional behavior of a phosphonite ligand. Under the same reactiontemperature (95° C.) and pressure, hydroformylation activity steadilydecreased from 11.70 to 3.87, and the N/I ratio steadily increased from1.70 to 2.40 when the Ligand/Rh molar ratio increased from 15:1 to 60:1

Examples 7 through 11 illustrate the desirable nature of Ligand “B”.Example 7 showed an activity of 1.80 and an N/I value of 2.09 for a 15:1Ligand/Rh ratio. As the ratio of Ligand/Rh increased to 60:1 under thesame reaction temperature and pressure, the activity increased to 6.41,and the N/I ratio decreased to 1.83 (Example 9). The hydroformylationactivity increased to 8.20 even when the Ligand to Rh ratio increased to180:1 (Example 11). Typically, the hydroformylation reaction would beinactive under such a high Ligand/Rh loading.

Examples 12 and 13 illustrate the desirable nature of Ligand “C”. Whenthe Ligand/Rh ratio increased from 15:1 to 30:1, the activity increasedfrom 0.19 to 0.25, and the N/I value increased from 2.79 to 2.81 underthe same reaction temperature and pressure.

Examples 14 through 16 illustrate the desirable nature of Ligand “D”.When the Ligand/Rh ratio increased from 15:1 to 60:1, the activityincreased from 5.44 to 7.03, and the N/I value increased from 1.53 to1.57 under the same reaction temperature and pressure.

The invention has been described in detail with particular reference topreferred embodiments and illustrative examples thereof, but it will beunderstood that variations and modifications can be effected within thespirit and scope of the invention.

1. A phosphonite compound having the structure of formula (I):

wherein R is an alkyl, cycloalky or aryl group which is substituted orunsubstituted and which contains 1 to 30 carbon atoms; Ar₁ and Ar₂ areeach independently selected from aryl groups which are substituted orunsubstituted and which contain 4 to 30 carbon atoms; R1 to R4 are eachindependently selected from H and alkyl, cycloalkyl, and aryl groupswhich are substituted or unsubstituted, and which contain 1 to 40 carbonatoms; and R5 and R6 are each independently selected from substituted orunsubstituted cycloalkyl, aryl-substituted alkyl, cycloalkyl-substitutedalkyl and substituted or unsubstituted aryl groups, wherein R5 and R6each contain up to 40 carbon atoms; and X is (i) a chemical bonddirectly between ring carbon atoms of each aromatic group, (ii) aheteroatom, or (iii) a group having the formula

wherein R15 and R16 are each independently selected from hydrogen andalkyl or aryl having up to 10 carbon atoms.
 2. The compound according toclaim 1, wherein Ar₁ and Ar₂ are each independently selected from arylgroups having the structure of formulas (XI)-(XIII):

wherein R13 and R14 are independently selected from alkyl, alkoxy,halogen, cycloalkoxy, formyl, alkanoyl, cycloalkyl, aryl, aryloxy,aroyl, carboxyl, carboxylate salts, alkoxy-carbonyl, alkanoyloxy, cyano,sulfonic acid, and sulfonate salts; x is an integer from 0 to 5; and yis an integer from 0 to
 7. 3. The compound according to claim 2, whereinR13 and R14 are independently selected from alkyl having 1 to 10 carbonatoms, and x and y are independently 0, 1, or
 2. 4. The compoundaccording to claim 1, which has the following structure (B):


5. A catalyst solution comprising: (a) a phosphonite compound; (b) aGroup VIII metal or rhenium; and (c) a hydroformylation solvent, whereinsaid phosphonite compound has the structure of formula (I):

wherein R is an alkyl, cycloalky or aryl group which is substituted orunsubstituted and which contains 1 to 30 carbon atoms; Ar₁ and Ar₂ areeach independently selected from aryl groups which are substituted orunsubstituted and which contain 4 to 30 carbon atoms; R1 to R4 are eachindependently selected from H and alkyl, cycloalkyl, and aryl groupswhich are substituted or unsubstituted, and which contain 1 to 40 carbonatoms; and R5 and R6 are each independently selected from substituted orunsubstituted cycloalkyl, aryl-substituted alkyl, cycloalkyl-substitutedalkyl and substituted or unsubstituted aryl groups, wherein R5 and R6each contain up to 40 carbon atoms; and X is (i) a chemical bonddirectly between ring carbon atoms of each aromatic group, (ii) aheteroatom, or (iii) a group having the formula

wherein R15 and R16 are each independently selected from hydrogen andalkyl or aryl having one to 10 carbon atoms.
 6. The catalyst solutionaccording to claim 5, wherein Ar₁ and Ar₂ are each independentlyselected from aryl groups having the structure of formulas (XI)-(XIII):

wherein R13 and R14 are independently selected from alkyl, alkoxy,halogen, cycloalkoxy, formyl, alkanoyl, cycloalkyl, aryl, aryloxy,aroyl, carboxyl, carboxylate salts, alkoxy-carbonyl, alkanoyloxy, cyano,sulfonic acid, and sulfonate salts; x is an integer from 0 to 5; and yis an integer from 0 to
 7. 7. The catalyst solution according to claim6, wherein R13 and R14 are independently selected from alkyl having 1 to10 carbon atoms, and x and y are independently 0,1, or
 2. 8. Thecatalyst solution according to claim 5, wherein the phosphonite compoundhas the following structure (B):


9. The catalyst solution according to claim 5, wherein the Group VIIImetal is rhodium.
 10. The catalyst solution according to claim 9, whichcomprises from about 20 to 300 mg/l of rhodium, and a ratio of grammoles of phosphonite to gram atom of rhodium of about 1:1 to 200:1. 11.The catalyst solution according to claim 8, wherein the Group VIII metalis rhodium.
 12. The catalyst solution according to claim 11, whichcomprises from about 20 to 300 mg/l of rhodium, and a ratio of grammoles of phosphonite to gram atom of rhodium of about 1:1 to 200:1. 13.The catalyst solution according to claim 5, wherein the hydroformylationsolvent is selected from alkanes, cycloalkanes, alkenes, cycloalkenes,alcohols, esters, ketones, acetals, ethers, aldehydes, water, andmixtures thereof.
 14. A process for preparing aldehydes, comprisingcontacting an olefin with hydrogen and carbon monoxide, underhydroformylation conditions, in the presence of the catalyst solution,the catalyst solution comprising: (a) a phosphonite compound; (b) aGroup VIII metal or rhenium; and (c) a hydroformylation solvent, whereinsaid phosphonite compound has the structure of formula (I):

wherein R is an alkyl, cycloalky or aryl group which is substituted orunsubstituted and which contains 1 to 30 carbon atoms; Ar₁ and Ar₂ areeach independently selected from aryl groups which are substituted orunsubstituted and which contain 4 to 30 carbon atoms; R1 to R6 are eachindependently selected from H and alkyl, cycloalkyl, and aryl groupswhich are substituted or unsubstituted, and which contain 1 to 40 carbonatoms; and X is (i) a chemical bond directly between ring carbon atomsof each aromatic group, (ii) a heteroatom, or (iii) a group having theformula

wherein R15 and R16 are each independently selected from hydrogen andalkyl or aryl having one to 10 carbon atoms.
 15. The process accordingto claim 14, wherein Ar₁ and Ar₂ are each independently selected fromaryl groups having the structure of formulas (XI)-(XIII):

wherein R13 and R14 are independently selected from alkyl, alkoxy,halogen, cycloalkoxy, formyl, alkanoyl, cycloalkyl, aryl, aryloxy,aroyl, carboxyl, carboxylate salts, alkoxy-carbonyl, alkanoyloxy, cyano,sulfonic acid, and sulfonate salts; x is an integer from 0 to 5; and yis an integer from 0 to
 7. 16. The process according to claim 15,wherein R13 and R14 are independently selected from alkyl having 1 to 10carbon atoms, and x and y are independently 0, 1, or
 2. 17. The processaccording to claim 14, wherein the phosphonite compound has thefollowing structure (B):


18. The process according to claim 14, wherein the Group VIII metal isrhodium.
 19. The process according to claim 18, wherein the catalystsolution comprises from about 20 to 300 mg/l of rhodium, and a ratio ofgram moles of phosphonite to gram atom of rhodium of about 1:1 to 200:1.20. The process according to claim 17, wherein the Group VIII metal isrhodium.
 21. The process according to claim 20, wherein the catalystsolution comprises from about 20 to 300 mg/l of rhodium, and a ratio ofgram moles of phosphonite to gram atom of rhodium of about 1:1 to 200:1.22. The process according to claim 14, wherein the hydroformylationsolvent is selected from alkanes, cycloalkanes, alkenes, cycloalkenes,alcohols, esters, ketones, acetals, ethers, aldehydes, water, andmixtures thereof.
 23. The process according to claim 14, wherein thehydroformylation conditions comprise a temperature ranging from 75 to125° C. and a pressure from atmospheric to 70 bars absolute (about 15 to1,000 psig).
 24. The process according to claim 14, wherein the olefinis propylene, and the aldehydes comprise normal- and iso-butyraldehyde.25. The process according to claim 17, wherein the olefin is propylene,and the aldehydes comprise normal- and iso-butyraldehyde.